Lucky day for you! I have spent a considerable amount of time writing posts about the First World War over the past year or so and I've kept track of them! Here is a direct link to all of them and it should serve you as a great place to start. These are not quotable sources, they are not a replacement for textbooks. However they are well researched and come from quite a number of academic works I own and should serve as a general overview.

Out of these, these in particular can get you going:

• Why was WWI considered "inevitable"?

• What was the endgame of central powers in World War I?

• Could you describe the "starting position" for each of the major players right before the assassination of the Archduke?

• Prior to the start of trench warfare, how were the initial battles of WWI conducted? // Also on German war crimes in Belgium

• On "Lions led by Donkeys" and "stupid soldiers" in the opening of the war

• How far did the front line move on the Western Front?

• Is it true that miners were happy to fight in the trenches in WWI because conditions were better?

• Why did the Germans surrender in WWI?

• Was it known or suspected that the Treaty of Versailles would lead to the economic collapse of post WWI Germany?

• There a lot of posts in /r/badhistory about WWI being a "useless" and "pointless" war. This idea seems to be ingrained in the popular memory of the war, what do you say to people who argue it was indeed "useless"?